Apparatus for examining a body of living tissues

ABSTRACT

An apparatus for the examination of living tissues, comprises an illuminator (228) for illuminating the tissue with infra-red-containing electromagnetic radiation, a television camera (202) for receiving the radiation which is transmitted through the tissue and image devices (216) for producing an image of the received radiation. In addition a probe (224) is provided for applying ultrasound to a region of the tissue and for receiving the reflected ultrasonic signals from the region. The signals obtained are representative of the velocity of blood flow in the region and a computer (216) is provided for generating from the signal an image which provides an indication of blood flow velocity in the region. The apparatus further comprises an arm rotatably mounted on a support about a pivot, the television camera (202) being mounted on the arm on one side of the pivot. A device for holding the tissue to be imaged by the television camera is mounted on the arm on the other side of the pivot.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for the examination of abody of living tissues. In particular, the present invention relates toan apparatus for telediaphanographic and ultrasonic investigation foruse in the detection and diagnosis of cancer, and particularly breastcancer in women. The present invention further relates to an apparatusfor imaging a body of living tissues.

It is now widely recognised that repeated use of X-ray mammography isvaluable in the detection of breast cancer for women over 50 years butthat in younger women aged less than 50 years where no benefits havebeen demonstrated the risk/benefit ratio is negative. In addition, inthe young (<50 years) dense breast X-ray mammography misses asignificant proportion of cancers and other tumours when used as adiagnostic technique. It is thus widely recognised that for screeningand for diagnosis new, preferably more accurate and risk free techniquesare desirable to detect breast cancer at an early stage before thedisease is disseminated to other organs. The Forrest Report published inthe United Kingdom in 1987 recommends screening at 3 yearly intervals byX-ray mammography of women over 50 years. The interval is chosen tominimise economic costs and to limit cumulative X-ray dose to breasttissues as it has been reported that X-rays can themselves cause cancerand that the breast is an especially sensitive organ.

GB-A-2092856, GB-A-2111794, U.S. Pat. No. 4,600,011 and EP-A-0108617(each of which are in the name of the present applicant and thedisclosures of which are incorporated herein by reference) relate tooptical methods of detecting breast cancer (and other cancers) usingoptical (non-ionising) radiation but even these methods have only shownsensitivity of about 0.9 for palpable lesions. In other words about 10%of tumours are missed or wrongly interpreted.

It is also known to attempt to detect breast cancer by using Dopplerultrasound techniques. Two documents which disclose such techniques are"The Scattering of Ultrasound by Blood Flowing in Tumours" by P.N.Burns, PhD. Thesis, University of Bristol, 1985 and "Tumour Detection byUltrasonic Blood Flow Signals" by P.N.T. Wells et al, (1977) Ultrasonics(15); p. 231-232. Such methods detect blood flow changes at theadvancing front of breast carcinoma. The signals from the associatedvolume of neovascularization differ from those obtained when normaltissues are interrogated. The flow velocity and the quantity of bloodflowing are generally higher near a malignant tumor. The ultrasoundDoppler data is normally presented in an isometric display andcomparison made of the signals close to and far away from the suspectedtumour. When Doppler ultrasound is used by itself as a breast screeningtechnique every cubic centimetre of tissue must be separatelyinterrogated and analysed. With a single transducer (of area typically 1cm²) the method is very time consuming and required considerablecomputer memory, (typically more than provided by a microcomputer), togenerate the isometric displays.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for the examination of abody of living tissues, the apparatus comprising means for illuminatingthe body of living tissues with infra-red-containing electromagneticradiation, means for receiving electromagnetic radiation which istransmitted through the body of living tissues, means for producing animage of the received radiation, means for applying ultrasound to aregion of the body of living tissues, means for receiving reflectedultrasonic signals from the region, characterised by means for producinga signal which is representative of the velocity of blood flow in theregion and means for generating from the signal a graphicalrepresentation which provides an indication of blood flow velocity inthe region.

Preferably, the means for receiving electromagnetic radiation comprisesa television camera and the apparatus further comprises a support, anarm rotatably mounted on the support about a pivot, the televisioncamera being mounted on the arm on one side of the pivot, a holdingdevice for holding the body of living tissues to be imaged by thetelevision camera, the holding device being mounted on the arm on theother side of the pivot and a wavelength selector means for selectingthe wavelength of infra-red radiation incident on the body of livingtissues whereby the incident radiation is in a selected one of a seriesof pass-bands.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic illustration of part of an apparatus forexamination of a body of living tissues in accordance with a firstembodiment of the present invention;

FIG. 2 is a diagrammatic illustration of an apparatus for examination ofa body of living tissues in accordance with a second embodiment of thepresent invention;

FIG. 3 is a perspective view of an imaging assembly of the apparatus forexamination of a body of living tissues; and

FIG. 4 is an enlarged cross-sectional view through an illuminationsystem of the imaging assembly of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, an apparatus for examination of a body of livingtissues comprising a television camera 2 which is sensitive towavelengths in the infra-red region of the electromagnetic spectrum, andin particular to the near infra-red. Typically, the camera 2 issensitive to wavelengths ranging from 400 to 1200 nanometers. The camera2 is connected to a frame store 4 which is adapted to store images whichare received by the camera 2. A monochrome monitor 6 is connected to theframe store 4 and is adapted to display a monochrome image which isdetected by the camera 2. A video digitiser 8 is also connected to theframe store 4. The video digitiser 8 is adapted to convert the analoguevideo signals which are stored in the frame store 4 into digital formfor subsequent processing. The output of the video digitiser 8 passes toa first input 10 of a two way switch 12. The output 14 of the two wayswitch 12 is connected to a microcomputer 16 which is programmed toprocess the digital signals from the video digitiser 8, in a mannerwhich is described in more detail below, and to produce colour-coded(pseudo-colour) images. Those images may be reproduced by a colourmonitor 18 and/or a colour printer 20, both of which are connected tothe microcomputer 16. One or more disk drives 22 are also connected tothe microcomputer 16 for storage of image information.

The foregoing elements comprise a telediaphanographic system which canbe used to image female breasts in the investigation of breast disease.

In accordance with the present invention, the telediaphanographic systemis coupled with a Doppler ultrasound system for detecting malignanttumours in the female breast. The Doppler ultrasound system includes aDoppler ultrasonic transducer 24. The ultrasonic transducer 24 iscylindrical and is provided at one end thereof with a semi-circularultrasonic transmitter 26 and a semi-circular ultrasonic receiver 28.The ultrasonic transmitter 26 is excited at its resonant frequency by anoscillator (not shown). The ultrasonic transducer 24 is connected to aDoppler module 30 which amplifies the received signal from the receiver28 and produces a frequency difference signal (the Doppler signal) bymixing the received signal with the signal from the oscillator. TheDoppler signal is outputted, in turn, to an audio amplifier 32 and anaudio digitiser 34 which outputs a digital signal representing theDoppler shift and this digital signal is fed to a second input 36 of thetwo way switch 12. The two way switch 12 is adapted selectively to beswitched between its two inputs 10, 36 depending on whether atelediaphanographic image or a Doppler image is to be displayed.

FIG. 2 illustrates a second embodiment of an apparatus for examinationof a body of living tissues. The apparatus comprises a video camera 202which has a highly sensitive extended red (ER) Newvicon tube whichpermits imaging into the near infra-red region, up to 1000 nm, with goodlow light performance. The camera 202 may be provided with a zoom lenshaving a range from 17.5 mm to 105 mm. The camera 202 is connected to aframe store 204. The video signal from the camera 202 passes directly tothe input of the frame store 204 and the signal is sampled in real timeand held in a frame buffer of 512×512 pixels (8 bit/pixel). The framebuffer output is reconverted to an analog signal and is routed via aslow-scan converter to a monochrome monitor 206. An image in the framestore can be frozen by pressing a foot switch 205 which is a latchingswitch and must be pressed again to unfreeze the frozen image. A videodigitiser 208 converts the analog output of the frame store 204 into asuitable digital form for input to the computer 216 via a selector unit212. The video digitiser 208 employs a simple slow-scan system, togetherwith proprietary software, and provides two conversion options (a) lowresolution of 320×200 pixels, having a conversion time of 16 seconds,and (b) high resolution of 640×400 pixels having a conversion time of 45seconds. A Doppler blood flow detector 224 together with its associatedDoppler module 230 acts as a "stand alone" unit which is connected to anaudio digitiser 234 which in turn is connected to the selector unit 212.The Doppler unit is powered from an internal rechargable battery. TheDoppler module 230 includes a small loudspeaker (not shown) and in usethe Doppler blood flow signals can be heard from the small loudspeaker.Amplification is provided by an AC coupled amplifier with variablefeedback gain control. The low frequency cut-off is 300Hz and the gainrange allows for an input signal from 400 mVpp to 6Vpp. The Dopplerprobe 224 operates at a nominal frequency of 8MHz and a power of lessthan 85 mW/cm.sup. 2. The maximum intensity in tissue is 64 mW/cm². Theaudio digitiser 234 acts to digitise the signal from the externalDoppler blood flow detector. The maximum number of samples is limited to80000. The sampling rate can be varied but the default value on start-upis 8000 samples per second, this giving an analysis range of from 0 to4000 Hz which is adequate for most blood-flow velocities. A higher valuemay be chosen if frequency shifts greater than 4000 Hz are expected. Theupper limit to sampling frequency is 20000, and the higher the samplingfrequency the shorter the overall recording time. The audio digitizer234 amplifies the signal and passes through a fourth order anti-aliasfilter (having a cut off at 8KHz) to an analog to digital converter. Theresolution is 8-bit and the sampling frequency is selectable up to20KHz. The selector unit 212 permits switching of a parallel port of thecomputer 216 between the video digitiser 208, the audio digitiser 234and a printer 220 which is connected to the selector unit 212. Inpractice, the selector unit 212 incorporates the audio digitiser 234with the audio input connector and an amplitude control. The computer216 has a parallel port (not shown) which acts as an output port for theprinter 220 and an input port for both the audio and video digitisers234, 208. A colour monitor 218 is connected to the computer 216 and thecomputer 216 is also provided with a keyboard 224 and a mouse 226. Thecomputer is provided with appropriate disc drives (not shown). Theoperation of the computer 216 is governed by software which controls allthe functions of taking an image, storing it, and retrieving it forsubsequent examination. The images taken are either video images orDoppler images. The software can either be adapted to give lowresolution or high resolution images on the colour monitor 218 and onthe printer 220. The software can also be adapted to given pseudo-colourimages or greyscale images.

The apparatus also incorporate a torch 228 for transluminating thebreast 240 of a patient. The torch 228 is connected to a variablebrightness control 230 which in turn is connected to a suitable powersupply 232. In practice, two torches are employed. One torch includes aheat absorbing filter and is intended for visual inspection of thetissues to be imaged by the camera. The heat absorbing filter permitsthe torch to be used for relatively long periods of time, i.e. up toabout 5 minutes, while the operator examines the patient visually todetermine whether or not there are any abnormalities in the breast. Thesecond torch is not provided with a heat absorbing filter and isintended to be used for short periods of time only while the breast isbeing imaged by the camera 202. Each torch includes a quartz halogenlamp which emits high intensity radiation which includes infra-redradiation.

In use, the patient is seated and the camera 202 is arranged so that itis pointing at the breast 240 to be examined and is about 1.3 to 1.5meters from the breast. The camera 202 is adjusted so that a good imageof the breast appears on the monochrome monitor 206. A torch 228 whichincludes a heat absorbing filter is placed against the underside of thebreast as shown in FIG. 2. The variable brightness control 230 isadjusted for maximum brightness and the breast is examined visually bythe operator for any clear abnormality by moving the torch as required.If an abnormality is revealed, a second torch which does not include aheat absorbing filter is placed against the breast so as to illuminatethe abnormality. The torch brightness control 230 and the lens apertureof the camera 202 are adjusted to obtain the best image on themonochrome monitor 206. The image in the frame store 204 is frozen bypressing the foot switch 205. The image on the monitor 206 may then beexamined and this process may be repeated until an image suitable forrecording is obtained. If desired, a photograph may be taken of theimage on the monochrome monitor 206 by a camera (not shown). The storedimage is then transferred to the computer by way of the video digitiser208 and the selector unit 212, the latter being switched to anappropriate video position. The image is then stored on a floppy discfor the computer 216 and is shown on the colour monitor 218. Thekeyboard 224 may be employed to type in appropriate bibliographicinformation relating to the image. If a suspicious area of increasedlight absorption in the breast has been identified using the torches228, the area can be further investigated using the Doppler probe 224.The selector unit 212 is switched to a Doppler position and the Dopplerblood flow detector 224, 230 is switched on. Acoustic coupling jelly isapplied to the end of the Doppler probe 224 and the tip is placedagainst the area of the breast to be investigated. The direction of theprobe is adjusted until a distinctive, time varying sound is heard. Ifno such sound is heard then this suggests that there is no blood flowingin the region under investigation and that malignancy is unlikely. If asound is obtained, the software of the computer is switched into Dopplermode and a Doppler spectrum can be displayed on the colour monitor 218after appropriate analysis by the computer 216 of the digital signalfrom the audio digitiser 234. Initially, the Doppler signal is displayedon the colour monitor 218 in "oscilloscope" fashion. Then, the Dopplersignal is analysed by the computer software using a Fast FourierTransform Technique. The spectral analysis of the Doppler signal therebyproduced is displayed on the monitor as a series of intensity againstfrequency graphs arranged in an isometric form to give a "3D"representation of the time course of the spectrum. Also displayed is asecond representation of the Doppler signal wherein intensity ispresented as a darkened area with frequency as the vertical axis andtime as the horizontal axis. This is referred to as a "Velograph"display and is used to study the time-course of the maximum frequency.The Doppler data can be recorded on floppy disc for subsequentretrieval. In addition, the Doppler spectrum can also be printed by theprinter 220.

FIG. 3 shows an imaging assembly 38 which includes a television camera302, which is sensitive to wavelengths in the near infra-red region ofthe electromagnetic spectrum and is the same as that illustrated inFIGS. 1 and 2, and an infra-red radiation source and also a device forholding the body of living tissues to be examined. The holding device isparticularly adapted to hold a female breast for the purpose of breastscanning for detecting breast cancer.

The image assembly 38 includes a base 40, which permits the imagingassembly 38 to be free-standing, and an upright support 42 which ismounted on the base 40. One the front face of the support 42 is fixed aguide member 44 which has two opposed channels 46 therein which areprovided on respective sides of the support 42. A sliding member 48, isslidably mounted on the front face 50 of the guide member 44 and extendsinto the opposed channels 46 so that the sliding member 48 is heldcaptive on, but can freely slide up and down, the guide member 48. Awire 52 is fixed to the top of the sliding member 48, passes over apulley 54 which is mounted at the top of the guide member 44 and extendsdownwardly into an elongate upright cavity between the guide member 44and the support 42. A counterbalance weight (not shown) is attached tothe free end of the wire 52. This counterbalance arrangement permits thesliding member 48 easily to be slid up and down the guide member 44. Anarm 54 is mounted on a pivot 56 which is provided on the front face 58of the sliding member 48. The pivot 56 is provided with a clamp 60 whichpermits the arm 54 to be clamped in any rotational position. The clamp60 can be unclamped to permit the arm 54 to be freely rotated to anyother desired rotational position. A camera mount 62 is provided at oneend of the arm 54. The camera 302 is attached to the camera mount 62 andis directed towards a device 64 for holding the body of living tissuesto be examined, the holding device being provided at the other end ofthe arm 54. The camera 302 can be moved over an arc 66 of about 5° so asto permit stereoscopic images to be obtained.

The device 64 for holding the body of living tissues to be examined isprovided on the arm 54 on the other side of the pivot 56 and comprises atransparent bottom plate 68, which faces the camera 2 and whose distancefrom the camera 302 is fixed, and a transparent top plate 70 which isparallel to the bottom plate 68, is nearer to the camera 302 than thebottom plate 68, and can be moved towards or away from the bottom plate68 thereby to vary the spacing between the two plates 68, 70. The topplate 70 is rectangular and includes an upwardly curved edge 72 which isremote from the support 42 and is adapted, in use, to bear against thechest of a female patient whose breasts are being examined. The topplate 70 is mounted in a 3-sided frame 74 which supports the other threesides of the top plate 70. The top plate 70 can be slid laterally out ofthe frame 74. The frame 74 is fixed to one end of a scissors jack 76,the other end of which is fixed to a mount 78 which is attached to thearm 54. A pair of parallel struts 80 extend between the mount 78 and asecond mount 82 which is located adjacent the bottom plate 68. The frame74 is slidably mounted on the struts 80. The top plate 70 can be movedtowards and away from the bottom plate 68 by extending and compressingthe scissors jack 76.

The bottom plate is provided in the top of a housing 84 for anillumination system which is shown in greater detail in FIG. 3. Thehousing 84 is fixed to the arm 54 and includes an opening 86 in theupper surface thereof over which the bottom plate 68 is disposed. Thebottom plate 68 is arranged to be slidable towards and away from the arm54 by being held between two guide strips 88. A variable aperture 90 isprovided in the bottom plate 68 and fixed to the bottom plate 68 beneaththe variable aperture 90 is a light guide 92 which includes a prism, 94preferably of perspex, which has a reflecting face at 45° to the bottomplate 68. At an input end of the light guide 92 is disposed a box 96containing a source 98 of infra-red radiation and a series of filters100. The source 98 of infra-red radiation may be a 12 volt light sourceor a laser having a wavelength range of 400 to 1200 nanometers, thelaser optionally being tunable. The filters 100 are a series of spacedplates which are held by filter support 102. The filter support 102 hasa plurality of pairs of opposed channels 104, each filter 100 beingslidably mounted in a respective pair of channels 104. A respectivehandle 106 is attached to each filter 100 and the series of handles 106extends out of the housing 84 through an elongate slot 108 which isparallel to the bottom plate 68. The handles 106 can selectively be slidin and out of the housing 84 thereby to position the respective filters100 in front of or away from the source 98 of infra-red radiation. Thehandles 106 can also be slid along the slot 108 thereby to move thewhole assembly of the bottom plate 68, the light guide 92, the box 96containing the source 98 of infra-red radiation and the filters 100towards and away from the arm 54. A cooling fan 110 is also disposed inthe housing 84 for removing warm air which has been heated by the source98 of infra-red radiation.

It will be seen that by rotating the arm 54 the holding device 64 can berotated to any desired position and this, coupled with the permittedmovement of the illumination system towards and away from the patient bysliding of the handles 106 toward and away from the arm 54, permits thebreast to be examined in any desired orientation. In addition, byvarying the distance between the lower and upper plate 68, 70, a breastof any size can be firmly held between the plates 68, 70 for properexamination.

The operation of the apparatus of FIGS. 1, 3 and 4 will now bedescribed, although it will be apparent that the following descriptionalso applies to the embodiment of FIG. 2. The patient stands in front ofthe imaging assembly 38 and a breast to be examined is placed betweenthe two plates 68, 70 at the desired orientation and compressedtherebetween by operating the scissors jack 76. The room is placed indarkness and then the source 98 of infra-red radiation is switched on.Filters 100 having passed bands around 100 nanometers wide areselectively placed in front of the source 98 of infra-red radiation sothat the breast is illuminated with a succession of bands of infra-redradiation of increasing wavelength. This produces a succession ofimages, each of which is received by the camera 302 and recorded by theframe store 4. Each image is digitised by the video digitiser 8 and thenthe digitised signals are passed through the two-way switch 12 to themicrocomputer 16 which processes the signals to produce a set ofpsuedo-colour images of the breast. These psuedo-colour images arecombined to form a composite image which is displayed on the colourmonitor 18, printed by the colour printer 20, and recorded on the discdrive 22.

The composite psuedo-colour image has dark areas which coincide withregions in the breast of increase infra-red absorption. Those regionsmay correspond to regions of carcinoma in the breast. However, darkareas may also indicate the position of a bruise or a blood filled cystand this leads to ambiguities in the telediaphanographic results.

In order to resolve those ambiguities, and thereby accurately todiagnose the presence of cancerous regions, the top plate 70 is slid outof the frame 74 and the ultrasonic transducer 24 is placed on thebreast. The ultrasonic transducer 24 can be accurately positioned overthe suspected carcinoma by using the monochrome monitor 6 which shows animage of the dark region which is to be examined further and also animage of the ultrasonic transducer 24. When the ultrasonic transducer 24is correctly positioned over the advancing front of the suspectedtumour, the two-way switch 12 is switched over to input 36 and themicrocomputer 16 is switched, if necessary, to a programme whichprocesses digital signals from the audio digitiser 34.

The ultrasonic transducer 24 outputs a signal which is processed by theDoppler module 30, the audio amplifier 32 and the audio digitiser 34.The digital signal which is fed to the microcomputer 16 through thetwo-way switch 12 is representative of the frequency shift in the audiofrequency range of the Doppler signal. The magnitude of the frequencyshift is dependent upon the velocity of the red blood cells in theregion which is being interrogated. In the vascular region around atumour, the red blood cell velocity is relatively high and so there is arelatively large frequency shift. There is a distribution of velocitiesof the red blood cells and accordingly the digital signal which is fedto the microcomputer 16 is representative of data which has been sampledin a time domain. The microcomputer 16 analyses the data by Fouriertransform analysis to produce an isometric display in which the Z axisrepresents the amplitude; the X axis represents the velocity of flow andthe Y axis represents time. The isometric image is displayed on thecolour monitor 18, printed out by the colour printer 20 as stored in thedisk drives 22.

When an advancing front of a tumour is interrogated by the Dopplerultrasound apparatus, the amplitude and velocity demonstrate highervalues in the isometric image than in normal tissues away from thetumour, this being due to higher red blood cell velocity in the vascularregion of the advancing front of the tumour. The ultrasonic transducer24 is then used to obtain an isometric image at a contra-lateral site onthe patient, and by comparing the two isometric images obtained, onebeing at the periphery of the suspected lesion and the other being atthe contra-lateral site, evidence may be obtained as to the nature ofthe lesion. The image at the contra-lateral site will show reducedamplitude and velocity if no tumour is present at the contra-lateralsite.

The Doppler ultrasound system can detect regions of relatively highblood velocity, such as at the advancing front of tumours. However inbruises and blood filled cysts, such as those which may be present infemale breasts and which are detected using telediaphanography, there islittle or no blood flow and so these do not show up using Dopplerultrasound. Thus by combining telediaphonography and Doppler ultrasoundinterrogation procedures it is possible accurately to detect featuressuch as tumours, cysts and bruises and to distinguish between malignanttumours and benign features such as bruises and cysts.

The ultrasonic detector 24 may be adapted to operate at varyingultrasonic frequencies, typically 4, 8 or 12 megahertz. Sensitivity ofdetection increases with increasing frequency but the penetration depthof the ultrasound into the body decreases with increasing frequency(i.e. the attenuation of ultrasound by the body is greater at higherfrequencies). Accordingly, it is preferred to operate at 8 MHz in orderto compromise between sensitivity and depth of penetration. However, forthe examination of superficial lesions it may be preferable to usehigher ultrasonic frequencies and conversely for deep lesions it may bepreferable to use lower ultrasonic frequencies.

An advantage of the present invention is that it combines the twomethods of telediaphanography and Doppler ultrasound to achieve a highersensitivity and specificity for breast cancer than the known methods andalso reduces the time taken for Doppler ultrasound investigation totypically less than one minute.

The optical, (telediaphanography) method is applied first to identifyareas of increased light absorption which may be due to malignantdisease or to, for example, bruising or a blood filled cyst. Theselatter conditions may lead the clinician wrongly to conclude that abruise indicates a malignant change within the tissues.

If there is not a malignant change within the tissues interrogation withDoppler Ultrasound of the same region of tissues, thus identified, doesnot produce an abnormal isometric display and thus a bruise or othernon-malignant condition is correctly indicated. Without the use of anoptical telediaphanograpic method (prior to ultrasonic Dopplerinterrogation) the entire breast volume would have to be sampled withthe Doppler probe and any bruise, being a region where there is nomoving blood, would fail to be defined.

The preferred embodiment of the present invention also provides acompressor system which can compress the breast tissues at any angle andwhich utilises light in pass-bands typically 100 mm wide between 300 and1200 nm. The breast tissues are held stationary while a series ofoptical filters are interposed in the optical beam. A television camera,sensitive particularly in the near infra-red part of the electromagneticspectrum, rapidly detects a series of images which are digitised anddisplayed superimposed on a television monitor in different colours.Different pathologies are represented in the images by colour/shadevariations. The advantages of the arrangement are that small lesions arebetter resolved during compression and that the period of imagedigitisation may be several seconds. This process obviates the need for(costly) very rapid image capture. The optical filters may be engagedunder software control from the same microcomputer which displays imagesand analyses ultrasound data. When an image of a lesion is thusidentified a Doppler transducer, typically operating at 8MHz, is placedon the skin overlying the advancing front of the tumour and audiosignals generated by the blood flow recorded. These are digitised andused to generate isometric displays of blood flow velocity as a functionof time and amplitude of flow. By this combined method lesions arelocated and information about associated blood flow changes obtained allin the space of a few minutes. By way of comparison a Doppler study witha single small transducer would take much longer to produce definitiveresults and in any event would miss lesions where no abnormal flowoccurred (e.g. bruising or a cyst).

The combined approach disclosed herein which employs atelediaphanographic interrogation coupled with a Doppler ultrasoundinterrogation is quicker and more comprehensive then either method aloneand can provide required screening and diagnostic proceduresparticularly in the case of the young dense breast.

The present invention can provide a light-guided Doppler system whichcan achieve early detection and improved diagnosis of diseases(primarily) of the female breast.

It employs a novel combination of two previously distinct techniques inthe one instrument which can substantially contribute to the accuracy ofdiagnosis without the intrinsic hazards associated with X-RayMammography.

The system of the present invention can be employed as a complementarytechnique to X-Ray Mammography rather that a direct substitute. Howeverfollowing more extensive clinical trials it may prove to be superior ina number of pathologies and for certain subject groups.

As a result of the inventor's investigation, it is believed there are anumber of areas where the present invention may be more acceptable thanX-Ray Mammography.

(1) Radiologically dense breasts

(2) Young subjects

(3) Breasts with scar tissue

(4) Silicone augmented breasts

(5) Repeated follow-up subsequent to treatment

(6) Discharge from the nipple

(7) Subjects who refuse X-Ray

(8) Where the outcome of X-Ray is ambiguous

(9) Pregnant subjects

(10) Discrimination between benign and malignant tumours, cysts, bruisesand haematoma.

Although primarily intended as an instrument for the detection anddiagnosis of breast disease, the technique may also be applicable toother anatomical areas which are translucent in the visible and nearinfra-red spectrum.

It is also possible with the apparatus of the present invention tointerface an electronic stethoscope with the 2-way switch or selectorunit. The electronic stethoscope could be either additionally connectedto the 2-way switch or selector unit or substituted for the Doppler unitafter the Doppler signals have been recorded. In use, if audible Dopplersignals are obtained from an interrogated region of the breast, theelectronic stethoscope could subsequently be used to detectcharacteristic sounds of malignant tumours in that same region.

I claim:
 1. An apparatus for the examination of a body of livingtissues, the apparatus comprising means for illuminating the body ofliving tissues with infra-red containing electromagnetic radiation,means for receiving electromagnetic radiation which is transmittedthrough the body of living tissues, means for producing an image of thereceived radiation, means for applying ultrasound to a region of thebody of living tissues, means for receiving reflected ultrasonic signalsfrom the region, characterised by means for producing a signal which isrepresentative of the velocity of blood flow in the region and means forgenerating from the signal a graphical representation which provides anindication of blood flow velocity in the region.
 2. An apparatusaccording to claim 1 wherein the means for applying ultrasound and themeans for receiving reflected ultrasonic signals comprises an ultrasonicDoppler bloodflow detector.
 3. An apparatus according to claim 1 orclaim 2 further comprising a switching device to which the said meansfor receiving electromagnetic radiation and the said means for receivingreflected ultrasonic signals are connected, and a computer which isconnected to the switching device, the switching device beingselectively switchable between the said two receiving means thereby toselect which of the said two receiving means is connected to thecomputer.
 4. An apparatus according to claim 3 wherein the computer isadapted to process digital signals from the switching device and whereinthe means for producing an image and the means for generating agraphical representation comprise a common video monitor which receivesprocessed signals from the computer.
 5. An apparatus according to claim3 wherein the means for receiving electromagnetic radiation comprises atelevision camera which is sensitive to infra-red radiation and whereinthe television camera is connected to the switching device by a framestore and a video digitiser.
 6. An apparatus for the examination of abody of living tissues according to claim 1 wherein the means forreceiving electromagnetic radiation comprises a television camera, andwherein the apparatus further comprises a support, an arm rotatablymounted on the support about a pivot, the television camera beingmounted on the arm on one side of the pivot, a holding device forholding the body of living tissues to be imaged by the televisioncamera, the holding device being mounted on the arm on the other side ofthe pivot and a wavelength selector means for selecting the wavelengthof infra-red radiation incident on the body of living tissues wherebythe incident radiation is in a selected one of a series of pass-bands.